With increasing emergence of new techniques, 3GPP (3rd Generation Partnership Project) should consider how to keep its technical leading predominance in the field of mobile communication in the future ten years and to provide satisfactory supports for increasing requirements of operators and subscribers through sustaining evolvement and enhancement from wireless interface to core network in system architecture evolvement of the future mobile communication field. The evolution program of packet switched domain core network facing all IPs (System Architecture Evolution, SAE), which is now called as EPS (Evolved Packet System) is just originated under this background. The purpose of SAE is to “establish a 3GPP system frame structure with portability characterized in high data rate, low delay, data packetization and supporting a plurality of wireless access techniques”.
A SAE network has features including supporting end-to-end QoS (Quality of Service) assurance, all-around packetization, supporting multi-access technique, increase of supports for real-time services, network hierarchy flattening, etc. The SAE network further achieves separation of control plane data from user plane data, and a new network element of MME (Mobility Management Entity) has functions such as supporting roaming, authentication and bearing management as a network function entity for carrying user data on the control plane. The S6a interface between MME and HSS (Home Subscriber Server), as shown in FIG. 1, provides downloads of user data, authentication data, etc.
After initially accessing a network via different access networks, a user is required to register the location information of the user access point to its HSS before using network resources, and the HSS checks validity of the user. For a valid user, the HSS determines according to user subscription data whether to allow the user to use the network resources, and if the user is allowed to use the network resources, then related data information of the user (e.g., user subscription data, etc) is downloaded to the visited network where the user is located; for an invalid user, the HSS refuses the user using the network resources. Such a process is called as user registration, which mainly includes user location information registration and user data downloading process (if the user initially registers at the network or the user data stored in the access network are not reliable, and the like).
FIG. 2 is a flow chart of a user registering to the user's HLR (Home Location Register) through a SGSN (Service GPRS Supporting Node, which is a network element responsible for mobility management at the core network side) network node in accessing ways such as UTRAN (Universal Terrestrial Radio Access Network) or UMTS (Universal Mobile Telecommunication System), etc. in a packet switched domain. The Gr interface between a SGSN and a HLR is based on MAP network protocol, and the flow of user registration comprises the following steps:
Step 201, a user originating a network attaching request through an access network;
Step 202, a SGSN receiving the network attaching request of the user and detecting that the user is initially attached to the network and the MME has no user data information, the SGSN configuring a user subscription data downloading indicator and originating an Update Location Request (ULR) message based on MAP network protocol to the user's HLR, wherein the request message carries the user subscription data downloading indicator;
Step 203, the user's HLR checking the user, and triggering downloading of user data according to the user subscription data downloading indicator, if it is not necessary to download user data, then skipping step 204 and step 205 and directly returning an Update Location Ack message; if it is necessary to download user data, then executing step 204 and step 205 to download user data, wherein the process of downloading user data may be executed for a plurality of times;
Step 204, the HLR sending a data inserting request message to the SGSN, wherein the message includes information such as user subscription data;
Step 205, the SGSN checking user data and returning an data inserting ack message to the HLR, wherein the ack message includes subscription data that are not supported by the SGSN and the like;
Step 206, after receiving the data inserting ack message, the HLR executing a further action according to the result of data check, for example, restoring service data and the like; if user data are downloaded successfully, the HLR stores location information of user registration and returns an Update Location Ack message of success to the SGSN;
With the above steps, the process of user registration based on MAP network protocol between SGSN and HLR is completed, wherein step 202 and step 206 complete registration of user location information, step 204 and step 205 complete downloading of user data and verification/negotiation, so registration of user location information and download of user data and verification/negotiation are completed in one session.
FIG. 3 is a flow chart of a user registering to a HSS in an IP multimedia domain. FIG. 3 only describes the flow of user re-registration in order to describe user registration briefly, wherein I-CSCF (Interrogation Call Session Control Function) and S-CSCF (Serving Call Session Control Function) are two network elements used for session control in an IP multimedia domain and are access point of a core network and a service control point of user session respectively. The interface between I-CSCF and S-CSCF is based on SIP (Session Initial Protocol) network protocol, and the Cx interface between I-CSCF, S-CSCF and HSS is based on Diameter network protocol. The flow comprises the following steps:
Step 301, an I-CSCF receiving a SIP registration request from a visited network, knowing the user's HSS by inquiry, and then transmitting a user authorization request to the HSS;
Step 302, after receiving the user authorization request from the I-CSCF, the HSS directly returning name of a S-CSCF if it knows by inquiry that the user has registered at the S-CSCF;
Step 303, the HSS returning a user authorization ack message to the I-CSCF, wherein the ack message includes the name of the S-CSCF;
Step 304, the I-CSCF forwarding the SIP registration request to the S-CSCF;
Step 305, the S-CSCF processing the SIP registration request, transmitting a server allocating request to the HSS, and registering the user's location information and requesting to download user data;
Step 306, after receiving the server allocating request, the HSS checking whether the S-CSCF name is consistent with the stored S-CSCF name, allowing the user to register if it is, and returning a server allocating ack message for success, wherein the ack message includes the user data requested to download;
Step 307, the S-CSCF returning 200OK to the I-CSCF.
With the above steps, the user completes the process of registering in an IP multimedia domain, which involves a plurality of network elements, registration of location information and downloading of user data involved in user registration are completed in step 305 and step 306. With respect to implementation of a user registering to a HLR through a SGSN in a packet switched domain, the difference is that there is no process of negotiating on check result of user data between S-CSCF and HSS.
The user needs to implement user registration at the user's HSS via MME network node when the user intends to access a network in E-UTRAN (Evolved-UTRAN) accessing way in a packet switched domain. Function of a MME is similar to that of a SGSN, and the MME is a network node in a control plane which is mainly responsible for mobility management of a user in an EPS network. At present, it is definite that the S6a interface between a MME and a HSS adopts Diameter protocol, and processes of user registration vary in view of different data storage and data management of user data in different network domains. Since function of a MME is similar to that of a SGSN and incorporation of a MME network element is mainly based on evolvement of a packet switched domain, the functions completed in user registration between MME and HSS are similar to those completed in user registration between SGSN and HLR, i.e., not only registration of user location information but also downloading of user data and verification/negotiation of user data shall be completed.
However, implementation of user registration process based on MAP (Mobile Application part) network protocol cannot be totally mapped to a Diameter network protocol mainly due to the reason that the user session state machine in Diameter network protocol and that in MAP network protocol are different from each other. IETF (Internet Engineering Task Force) specifies that Diameter protocol must support Diameter basic protocol, in other words, S6a interface protocol must also comply with the state machines of client and server required by user session defined in Diameter basic protocol.
Diameter user session specifies that server may or may not be in session maintaining state. No matter it maintains session state or not, the working mechanism of a Diameter user session state machine is different from that of a MAP user session state machine. A MAP user session state machine allows a plurality of interactive requests to be originated between equivalent ends after a session is established, i.e., after receiving a session request from an equivalent end, a local end is allowed to transmit a session request to the equivalent end again during establishment of a session, and may returns a session response to the equivalent end after receiving a session response from the equivalent end. A Diameter user session state machine does not allow a client machine to receive requests from a server after the session is turned on, except a request for terminating the session, and only allows it to process acknowledgement messages from the server.
With the aid of a session state machine provided by MAP protocol, when a user registers in a visited domain network, its home domain network can implement capability information negotiation with the visited domain network. For example, when the user home domain network receives a user registration request message, it inserts user data into the visited domain network, and if insertion of user data fails, it returns a data insertion failure message, the user's home domain network forbids the user to register and returns a response message of registration failure to the visited domain network in which the user roams. If Diameter protocol is used, the HSS of the user's home domain network can only return a registration response message when receiving a user registration request message and user registration is considered as successful when a message of successful registration is returned.
Registration of a SGSN to a HLR based on MAP protocol includes registration of location information and downloading of user data as well as a process of data verification/negotiation, but this process requires a plurality of signaling interactions. IMS registration based on Diameter protocol, registration between S-CSCF and HSS only need one signaling interaction to implement registration of location information and downloading of user data, but lack the process of data verification/negotiation since HSS believes that the capability of S-CSCF selected by I-CSCF supports all user data, therefore the process of data verification/negotiation is not required.
To sum up, the problems of the prior art are as follows: the process of user registration implemented based on MAP network protocol in a packet switched domain cannot be used to implement user registration between MME and HSS based on Diameter network protocol in packet switched domain evolvement, and the existing flow of user registration implemented based on Diameter network protocol also does not apply to user registration between MME and HSS.